1. Field of the Invention
The present invention relates to a method for determining the moving mass of an elevator door system driven by a motor.
2. Description of the Related Art
Knowing the moving mass can be of interest in the case of drive tasks, for example, for the following reasons:    a) From safety aspects: for example, in accordance with the EN81 standard, the total kinetic energy of the door as it closes must not exceed either 4J or 10J,    b) for drive system reasons: if, for example, the force transmission must not exceed particular values, the acceleration can be matched to the moving mass,    c) for fault detection: if significant changes in mass arise, this may indicate faulty operating states and    d) for control system reasons: the controller parameters can be matched to the mass to achieve optimum running behavior.
To determine the moving mass, the following exemplary methods are known:    a) Apply a defined force and measure the resultant acceleration,    b) Apply a defined acceleration and measure the force required to produce the acceleration,    c) Apply a defined force for a defined time and measure the resultant speed,    d) Apply a defined voltage ramp and measure the current.
These methods require friction compensation and generally a defined running curve in order to minimize fault effects.
The last mentioned method is disclosed in EP 1 529 251 B1. With this method, the door system is moved by an electric drive device. As a prescribed maximum speed must not be exceeded here, the mass of the door system is automatically determined for configuring the door control unit. For this purpose, the door system is accelerated in a controlled manner during a monitored opening movement and possibly during a subsequent closing movement and then stopped again. The rms motor voltage of the drive device for determining the mass is obtained via the PWM voltage-time surfaces. Difficulties arise, however, as the voltage in the DC link may fluctuate and each output stage has a so-called dead time, i.e., times in which neither of the two transistors is in the on-state. In addition, purely electrical losses also occur in the motor line because of the line and internal resistance. All these effects considerably compromise determination of the power, and make it difficult to determine the mass in a largely automated manner and independently of the running curve.
EP 0 548 505 B1 also discloses a device and method for determining the dynamic mass. Here, however, the door has to be switched to a torque-free state for test purposes. The opening and closing movements required for test purposes are different from opening and closing movements during intended use which are herein referred to as intended opening and closing movements.